Liquid crystal display devices have undergone rapid development due to certain benefits, such as being lightweight, thin, and having low power consumption. In recent years, FFS (fringe field switching) mode has become well-known as a liquid crystal mode in liquid crystal display devices that are widely used in portable electronic devices such as smartphones, tablet PCs, and the like.
FFS mode liquid crystal display devices normally include: a substrate having a two-layer electrode structure; a substrate disposed so as to face the aforementioned substrate; and a liquid crystal layer of a horizontal orientation type that is sandwiched between the two substrates. The two-layer electrode structure includes: an upper electrode and a lower electrode formed from transparent conductive materials such as ITO (indium tin oxide) and IZO (indium zinc oxide); and an insulating layer sandwiched between these two electrode layers. A fringe electric field is then generated between the upper electrode and the lower electrode, and the liquid crystal layer is driven via this fringe electric field.
Research has also been conducted regarding liquid crystal display devices that use other types of liquid crystal modes. Patent Document 1, for example, discloses a liquid crystal display device in which: a liquid crystal layer formed of liquid crystal having a positive dielectric anisotropy is sandwiched between a pair of substrates disposed so as to face each other; a pixel electrode and a common electrode, which apply a vertical electric field to the liquid crystal layer, are respectively provided on an element substrate and an opposite substrate; and a comb-shaped electrode, which applies a horizontal electric field to the liquid crystal layer between the comb-shaped electrode and the pixel electrode, is provided above the pixel electrode on the element substrate with an insulating film therebetween.
In addition, Patent Document 2, for example, discloses a liquid crystal display device that has a color filter substrate and an array substrate on which thin film transistors have been provided at respective intersections of signal lines and scan lines arranged in a matrix. This liquid crystal display device has protrusions and recesses in a planarizing film on the array substrate side.